Windows 7 PCs Can Make Drives over 2.2 TB Attached through eSATA Appear Smaller

Windows 7 customers that connect a drive larger than 2.2 Terabytes through an eSATA port can experience some issues, Microsoft has warned.

It appears that the size of the drive will be reported as smaller to the actual space available to on the disk, the Redmond company noted, explaining that it’s not the fault of Windows 7, or that of Windows Vista, which can also experience similar problems.

But in addition to the size of the disk being reported incorrectly, there are additional issues.

“The disk may appear as the expected size if the drive is previously formatted using a different eSATA controller, USB, or 1394. In this scenario some read or write attempts may fail,” the software giant said.

In fact, the source of the problem according to Microsoft, is the way in which the controller driver reports the total number of sectors on the disk that is connected to the machine.

Effectively users will come across this issue in scenarios in which the number of sectors is underreported.

“Drives with more than 32-bits worth of sectors are reported using 32-bits, causing an artificially low disk size to be computed,” Microsoft explained.

“The SATA specification allows for up to 48-bits worth of sectors. Windows uses READ CAPACITY (10) and READ CAPACITY (16) to identify the number of sectors on the disk up to 64-bits worth.”

However, there are drives which will still return 32-bit info even though the number of sectors on disk is actually larger.

“Some SATA controller drivers return 32-bit sector information to READ CAPACITY (10) when there are more than 32-bits worth of sectors on the drive. These drivers should return 0xffffffff in this scenario and return the correct number of sectors to READ CAPACITY (16),” the company added.

Since Windows is not responsible for the issue, Microsoft does not provide an update or a hotfix designed to resolve the problem.

The software giant only advices customers to make sure that there are running the latest driver version from their SATA controller vendor.